STABILIZED INK COMPRISING SEMICONDUCTOR PARTICLES AND USES THEREOF

Abstract

An ink including at least one colloidal dispersion of particles and at least one metal halide binder, wherein the binder is a dissociated salt of metal and halogen. Also, a method for preparing a light-sensitive material, a light-sensitive material obtainable by the method, and a device including at least one light-sensitive material obtainable by the method.

Claims

1-15. (canceled)

16. An ink comprising: a) at least one colloidal dispersion of particles, said particles comprising a material of formula
M.sub.xQ.sub.yE.sub.zA.sub.w  (I) wherein: M is selected from the group consisting of Zn, Cd, Hg, Cu, Ag, Au, Ni, Pd, Pt, Co, Fe, Ru, Os, Mn, Tc, Re, Cr, Mo, W, V, Nd, Ta, Ti, Zr, Hf, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Cs or a mixture thereof; Q is selected from the group consisting of Zn, Cd, Hg, Cu, Ag, Au, Ni, Pd, Pt, Co, Fe, Ru, Os, Mn, Tc, Re, Cr, Mo, W, V, Nd, Ta, Ti, Zr, Hf, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Cs or a mixture thereof; E is selected from the group consisting of O, S, Se, Te, C, N, P, As, Sb, F, Cl, Br, I, F, or a mixture thereof; and A is selected from the group consisting of O, S, Se, Te, C, N, P, As, Sb, F, Cl, Br, I, F, or a mixture thereof; x, y, z and w are independently a decimal number from 0 to 5; x, y, z and w are not simultaneously equal to 0; x and y are not simultaneously equal to 0; z and w may not be simultaneously equal to 0; wherein the colloidal dispersion of particles further comprises at least one solvent and at least one ligand; b) at least one metal halide binder soluble in the colloidal dispersion a); wherein: the amount of particles in the ink is ranging from 1 to 40 wt % based on the total weight of the ink; the amount of solvent in the ink is ranging from 25 to 97 wt % based on the total weight of the ink; the amount of ligand in the ink is ranging from 0.1 to 8 wt % based on the total weight of the ink; and the amount of metal halide binder is ranging from 1 to 60% based on the total weight of the ink.

17. The ink according to claim 16, wherein the particles are semiconductor particles.

18. The ink according to claim 17, wherein the semiconductor particles are quantum dots.

19. The ink according to claim 18, wherein the quantum dots are core/shell quantum dots, the core comprising a different material from the shell.

20. The ink according to claim 16, wherein the amount of particles in the ink is ranging from 1 to 40 wt %, based on the total weight of the ink.

21. The ink according to claim 16, wherein the metal halide is selected from the group of ZnX.sub.2, PbX.sub.2, CdX.sub.2, SnX.sub.2, HgX.sub.2, BiX.sub.3, CsX, NaX, KX, LiX, CsPbX.sub.3 et HC(NH.sub.2).sub.2PbX.sub.3, CH.sub.3NH.sub.3PbX.sub.3, or a mixture thereof, wherein X is selected from Cl, Br, I, F or a mixture thereof.

22. The ink according to claim 16, wherein the colloidal dispersion of particles comprises at least one polar solvent selected from the group comprising formamide, dimethylformamide, N-methylformamide, 1,2-dichlorobenzene, 1,2-dichloroethane, 1,4-dichlorobenzene, propylene carbonate and N-methyl-2-pyrrolidone, dimethyl sulfoxide, 2,6 difluoropyridine, N,N dimethylacetamide, γ-butyrolactone, dimethylpropyleneurea, triethylphosphate, trimethylphosphate, dimethylethyleneurea, tetramethylurea, diethylformamide, o-Chloroaniline, dibutylsulfoxide, diethylacetamide, or a mixture thereof.

23. A method for preparing a light-sensitive material comprises the steps of: a) depositing an ink according to claim 16 onto a substrate; b) annealing deposited ink.

24. The method according to claim 23, wherein the deposited ink is annealed at a temperature ranging from 50° C. to 250° C.

25. The method according to claim 23, wherein the deposited ink is annealed during a period of time ranging from 10 minutes to 5 hours.

26. A light-sensitive material obtainable by the method according to claim 23.

27. The light-sensitive material according to claim 26, wherein said material is a continuous electrically conductive film comprising particles bound by a metal halide.

28. A device comprising at least one light-sensitive material according to claim 26.

29. The device according to claim 28, wherein said device comprises: at least one substrate; at least one electronic contact layer; at least one electron transport layer; and at least one photoactive layer comprising at least one light-sensitive material according to claim 26; wherein said device has a vertical geometry.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0548] FIG. 1 is a schematic representation of various shapes (spheres and plates) and structure (homostructure, core/shell, core/crown, dot in plate) of semi-conductive nanoparticles.

[0549] FIG. 2 is a schematic representation of an ink deposited and annealed according to the method of the invention and comprising particles 7 bound together by a metal halide binder 8.

[0550] FIG. 3 is a schematic representation of core/shell/shell particles.

[0551] FIG. 4A illustrates a device with vertical geometry according to an embodiment.

[0552] FIG. 4B illustrates a device with vertical geometry according to an embodiment.

[0553] FIG. 5 shows the normalized absorption spectrum of InAs/ZnSe quantum dots (dashed line) and an ink comprising InAs/ZnSe quantum dots and ZnCl.sub.2 binder (solid line). Abscissa axis is wavelength (nm), and ordinate axis is normalized absorbance (a.u).

[0554] FIG. 6A shows X-rays diffractogram of a film comprising PbS quantum dots and a mixture of CsI and PbI.sub.2 as the metal halide binder after annealing depending on annealing time (dashed peaks: PbS rock salt; from bottom to top diffractogram: 0-36 min, 36 min-1 h 12, 1 h 12-1 h 48, 1 h 48-2 h 24, 2 h 24-3 h). Abscissa axis is 20, and ordinate axis is counts (a.u).

[0555] FIG. 6B shows normalized absorption spectra of a film comprising PbS quantum dots and a mixture of CsI and PbI.sub.2 as the metal halide binder before annealing (dashed line) after annealing (solid line). Abscissa axis is wavelength (nm), and ordinate axis is normalized absorbance (a.u).

[0556] FIG. 7A shows IV curves of a film comprising PbS quantum dots and a mixture of CsI and PbI.sub.2 as the metal halide binder before annealing (solid line=dark, dashed line=1 mW/cm.sup.2, dash-dotted line=2 mW/cm.sup.2). Abscissa axis is applied voltage (V), and ordinate axis is current density (A/cm.sup.2).

[0557] FIG. 7B shows IV curves of a film comprising PbS quantum dots and a mixture of CsI and PbI.sub.2 as the metal halide binder after annealing (solid line=dark, dashed line=1 mW/cm.sup.2, dash-dotted line=2 mW/cm.sup.2). Abscissa axis is applied voltage (V), and ordinate axis is current density (A/cm.sup.2).

[0558] FIG. 8A shows x-rays diffractograms of a film comprising PbS quantum dots before and after annealing (dashed peaks: PbS rock salt; from bottom to top diffractogram: before annealing, after annealing). Abscissa axis is 20, and ordinate axis is counts (a.u).

[0559] FIG. 8B shows normalized absorption spectra of a film comprising PbS before (dashed line) and after annealing (solid line). Abscissa axis is wavelength (nm), and ordinate axis is normalized absorbance (a.u).

EXAMPLES

[0560] The present invention is further illustrated by the following examples.

Example 1: Ink Formulation—InAs/ZnSe Quantum Dots

[0561] In this example the ink comprises: [0562] a colloidal dispersion comprising InAs/ZnSe quantum dots, dimethylformamide (DMF) (as a solvent) and butylamine (as a ligand); and [0563] ZnCl.sub.2 as the metal halide binder.

InAs/ZnSe Quantum Dots Synthesis

[0564] In a three-neck flask, 400 mg of InCl.sub.3 and 800 mg of ZnCl.sub.2 are added in 15 mL of oleylamine. The solution is degassed at 115° C. for 1 hour. Under azote flow, 0.33 mL of As(NMe.sub.2).sub.3 are injected. After the injection, the solution is heated at 190° C. for 30 min. 1.5 mL of P(NEt.sub.2) are injected in the solution. The resulting mixture is heated at 230° C. for 1 h 15. ZnSe shell is formed by adding 800 mg of Zn(stear).sub.2 and slowly 1.1 mL of TOP-Se. The resulting solution is heated for 30 min. The temperature is cooled down.

[0565] The obtained InAs/ZnSe quantum dots are precipitated and dispersed in heptane.

Ligand Exchange with Metal Halide Binder

[0566] 250 μL of formic acid are added in 1.35 mL of InAs/ZnSe quantum dots dispersion. After removing the heptane, precipitated quantum dots are washed.

[0567] InAs/ZnSe quantum dots are dispersed in a solution containing 250 mg of ZnCl.sub.2 in 10 mL of DMF. Quantum dots are precipitated, dried under vacuum and dispersed in 250 μL of DMF and 15 μL of butylamine.

[0568] FIG. 5 shows the normalized absorption spectrum of InAs/ZnSe quantum dots and the ink comprising InAs/ZnSe quantum dots and ZnCl.sub.2 binder. One can observed that the absorption spectrum was not changed, proving that InAs/ZnSe quantum dots were not damaged during the ink formulation.

Example 2: Ink Formulation—PbS Quantum Dots

[0569] In this example the ink comprises: [0570] a colloidal dispersion comprising PbS quantum dots, dimethylformamide (DMF) and acetonitrile (as a solvent) and butylamine (as a ligand); and [0571] PbI.sub.2 and CsI as the metal halide binders.

[0572] 605 mg of lead iodide and 50 mg of sodium acetate are added in 10 mL of DMF. 10 mL of PbS quantum dots dispersed in heptane (12.5 mg.Math.mL.sup.−1) are added into DMF solution.

[0573] Sodium acetate promotes exchange from organic ligands to metal halide binder at the surface of PbS quantum dots.

[0574] After stirring, PbS quantum dots are transferred from the top heptane phase to the bottom DMF phase. After removing the heptane, PbS quantum dots solution is further washed.

[0575] PbS quantum dots are precipitated, dried under vacuum, then dispersed in 350 μL of DMF, in which 23 mg of cesium iodide were solubilized in advance. Then, 150 μL of acetonitrile and 10 μL of butylamine are added. The obtained ink is filtered (0.45 μm). The obtained ink comprises PbS quantum dots at a concentration of 250 mg.Math.mL.sup.−1.

Deposition of the Ink on a Substrate

[0576] The ink is deposited on a clean substrate by spin coating (1 layer, 4 minutes at 1000 rpm).

[0577] Table 3 below lists ink compositions that have been prepared using PbS quantum dots as particles.

TABLE-US-00003 TABLE 3 Quantum Metal dots % wt halide % wt Solvent % wt Ligands % wt PbS 10.7 PbI.sub.2 26.5 DMF/ACN 7/3 60.8 Butylamine 2 PbS 13.4 PbI.sub.2 + CsI 22.5 DMF/ACN 7/3 62.7 Butylamine 1.4 PbS 16.8 PbI.sub.2 + LiI 18.3 DMF/ACN 7/3 63.7 Butylamine 1.2 PbS 11.1 PbI.sub.2 + NaI 24 DMF/ACN 7/3 63.4 Butylamine 1.5 PbS 11.3 PbI.sub.2 + KI 22.3 DMF/ACN 7/3 65 Butylamine 1.4 PbS 16.9 PbI.sub.2 + CdI.sub.2 20.5 DMF/ACN 7/3 61.9 Butylamine 0.7 PbS 17 PbI.sub.2 + ZnI.sub.2 18.7 DMF/ACN 7/3 63.8 Butylamine 0.5 PbS 14.2 PbI.sub.2 + BiI.sub.3 16.1 DMF/ACN 7/3 69.7 Butylamine 1.8 PbS 10.2 PbI.sub.2 + SnI.sub.2 28.5 DMF/ACN 7/3 60.3 Butylamine 1 wherin DMF is dimethylformamide, and ACN is acetonitrile.

Example 3: Ink Formulation—PbS Quantum Dots

[0578] In this example the ink comprises: [0579] a colloidal dispersion comprising PbS quantum dots, dimethylformamide (DMF) and acetonitrile (as a solvent) and butylamine (as a ligand); and [0580] PbI.sub.2 and CsI as metal halide binders.

[0581] 605 mg of lead iodide, 370 mg of cesium iodide and 50 mg of sodium acetate are added in 10 mL of DMF. 10 mL of PbS quantum dots dispersed in heptane (12.5 mg.Math.mL.sup.−1) are added into DMF solution.

[0582] After stirring, PbS quantum dots are transferred from the top heptane phase to the bottom DMF phase. After removing the heptane, PbS quantum dots solution is further washed.

[0583] PbS quantum dots are precipitated, dried under vacuum, then dispersed in 350 μL of DMF, 150 μL of acetonitrile and 10 μL of butylamine. The obtained ink is filtered (0.45 μm). The obtained ink comprises PbS quantum dots at a concentration of 250 mg.Math.mL.sup.−1.

Deposition of Ink onto a Substrate

[0584] The ink is deposited on a clean substrate by spin coating (1 layer, 4 minutes at 1000 rpm). The deposited ink is annealed at 150° C. for 30 min.

[0585] The crystallographic structure and the optical features given by quantum confinement are preserved after this thermal treatment (see FIGS. 6A and B).

Test on Devices: Fabrication of IR Photodiode

[0586] i. Use pre-patterned ITO/glass substrate; [0587] ii. Clean ITO substrate with detergent, EtOH, acetone, and 2-propanol; [0588] iii. Warm substrate on hot plate at 110° C.; [0589] iv. Spin-coat TiO.sub.2 particle ink on the substrate at 5000 rpm for 30 seconds; [0590] v. Anneal on a hot plate at 450° C. for 30 minutes; [0591] vi. Cool down the substrate before next ink deposition; [0592] vii. Deposit the PbS ink; [0593] viii. Put the sample in vacuum in a thermal evaporation system; [0594] ix. Deposit 10 nm of a MoO.sub.3 thin film at 0.2 nm/second via thermal evaporation technique; [0595] x. Deposit 80 nm of an Au thin film at 0.2 nm/second via thermal evaporation technique to form the top electrode through a suitable shadow mask; [0596] xi. Obtain the final IR sensor based on multi-dot thin film; [0597] xii. Heat device to 150° C. for 1 to 3 hours.

[0598] The characterization includes I-V measurement in dark and under illumination conditions to extract the device performance such as the quantum efficiency and dark current;

[0599] In this example, the results showed that the performance exhibit no degradation after annealing (see FIGS. 7A and 6B).

Time Response

[0600] The temporal response of the device at high frequency is also characterized. The measurement is carried out by using a nanosecond pulsed laser source centered at 940 nm to illuminate the device and by using a 1 GHz high-speed transimpedance amplifier coupled with a 2 GHz high-bandwidth oscilloscope to measure the electronic response of the photodiode. In this example, the fabricated photodiode is polarized at −1V and is characterized with a 60 ns pulsed laser at 0.5 MHz frequency, with a pulsed power of 0.1 W/cm.sup.2. The temporal response of the device is measured before and after thermal treatment at 150° C. for 3 hours. The result shows that the fabricated device has a fast response performance with a rise time (t.sub.rise) of about 20 ns, and a fall time (t.sub.fall) less than 250 ns (with t.sub.rise and t.sub.fall define by the duration to reach 20% and 80% of the signal). Also, the response time shows no degradation after thermal treatment, indicating good thermal stability of the device and the photosensitive film. The measured response in this example is however limited by the capacitance of the fabricated device (with an active area of 0.45 mm.sup.2). This suggests that the temporal response of the device employing the photosensitive film in this invention could be even faster (at least down to few ns) if the active area of the device is reduced.

[0601] The following comparative examples demonstrate that the use of the ink of this invention into devices improve thermal stability of the photosensitive film.

Comparative Example 1: Using Ammonium Iodide as Ligands

[0602] 450 mg of lead iodide are added in 10 mL of DMF. 10 mL of PbS quantum dots dispersed in heptane (12.5 mg.Math.mL.sup.−1) are added into DMF solution.

[0603] After stirring, PbS quantum dots are transferred from the top octane phase to the bottom DMF phase. After removing the heptane, PbS quantum dots solution is further washed.

[0604] PbS quantum dots are precipitated, dried under vacuum, then dispersed in 350 μL of DMF, 150 μL of acetonitrile and 10 μL of butylamine. The obtained ink is filtered (0.45 μm). The obtained ink comprises PbS quantum dots at a concentration of 250 mg.Math.mL.sup.−1.

Deposition of Ink onto a Substrate

[0605] Same as Example 3

[0606] FIG. 8A, the emergence of new phase (Pb.sub.5S.sub.2I) is observed after annealing, proving that the PbS core structure has been modified during annealing. Moreover, optical features of the deposited ink are degraded after the thermal treatment (see FIG. 8B).

Test on Devices: Fabrication of IR Photodiode

[0607] Same as Example 3

[0608] The photocurrent is degraded after the annealing. This results from PbS core structure modification and deterioration during annealing.

Comparative Example 2: Using Lead Halides as Ligands

[0609] 575 mg of lead iodide, 91 mg of lead bromide and 40 mg of sodium acetate are added in 10 mL of DMF. 10 mL of PbS quantum dots dispersed in heptane (12.5 mg.Math.mL-1) are added into DMF solution.

[0610] After stirring, PbS quantum dots are transferred from the top heptane phase to the bottom DMF phase. After removing the heptane, QD solution is further washed.

[0611] PbS quantum dots are precipitated, dried under vacuum, then dispersed in 350 μL of DMF, 150 μL of acetonitrile and 10 μL of butylamine. The obtained ink is filtered (0.45 μm). The obtained ink comprises PbS quantum dots at a concentration of 250 mg.Math.mL.sup.−1.

Deposition of Ink onto a Substrate

[0612] Same as Example 3

Test on Devices: Fabrication of IR Photodiode

[0613] Same as Example 3

[0614] The performances of the device are degraded after the annealing. This results from PbS core structure modification and deterioration during annealing.

Comparative Example 3: Core/Shell PbS/CdS Quantum Dots

[0615] In a 100 mL three neck flask is introduced 22 mL of Cd(OA).sub.2 (0.35 M/ODE). The solution is degassed under vacuum at 110° C. during 1 h. Under azote flow, the temperature is set to 70° C. A solution of PbS quantum dots (50 mg.Math.mL.sup.−1) diluted with 6 mL of toluene are quickly injected in Cd(OAc).sub.2 solution. After 20 min of heating, 15 mL of heptane are added to quench the reaction.

[0616] PbS/CdS quantum dots are precipitated and dispersed in 6 mL of heptane.

Deposition of Ink onto a Substrate

[0617] Same as Example 3

[0618] The crystallographic structure is preserved during the annealing step. However, a blueshift is observed after the thermal treatment. It is the consequence of diffusion of Cd atoms from the shell in PbS core. Therefore, PbS/CdS don't exhibit thermal stability.

REFERENCES

[0619] 1—Core [0620] 11—Nanosphere core [0621] 12—Shell covering partially or totally a nanosphere core [0622] 13—Shell covering partially or totally a core/shell particle [0623] 2—Nanoplate [0624] 22—Nanoplate core [0625] 23—Crown [0626] 33—Nanoplate core [0627] 34—Shell covering partially or totally a nanoplate core [0628] 35—Shell covering partially or totally a core/shell particle [0629] 44—Nanosphere core [0630] 45—Shell covering partially or totally a nanosphere core [0631] 5—Device [0632] 51—Substrate [0633] 6—Photosensitive film [0634] 7—Particle [0635] 8—Metal halide binder